Contemporary HVAC systems are based on a combination of recycled air as well as the intake of ambient “clean and fresh” air that in reality may contain a variety of impurities and particulate matter, including pollutants, carcinogenic compounds, volatile organic compounds from vehicle exhaust, and a long list of toxic chemicals from any number of industrial sources. These impurities and particulate matter may be delivered by wind and precipitation, traveling from far distances, and contaminate the air and exterior spaces around the buildings. After airborne impurities and particulate matter enter a building, the concentration of such pollutants increases and may only be alleviated currently by the use of filters and similar devices. Recent data demonstrates that indoor contamination of pollutants can be up to seven times higher than outdoors.
Even such perceived “harmless” exhaust from a laundry dryer may contain up to 600 toxic chemicals, many and of them being carcinogenic coming from chemicals in detergents.
Conventional HVAC systems employ air cleaning devices such as dry electrostatic precipitators and filters that at best remove only dust particles, but do not remove or isolate the long list of pollutants identified above. Such conventional systems also require manual cleaning and periodic replacement of filter media. Such extensive maintenance makes the use of conventional systems impractical. Failure to clean these systems and/or to replace the filter media can drastically reduce the efficiency of these systems due to high pressure drop on the filters.
Existing HVAC systems circulate heated or cooled air from the air handling unit and return it back to the air handling unit, in both cases via registers located on the floors and walls. The current locations of such registers is not the optimum place for proper temperature control, as most energy losses take place at the windows and doors, where registers are not able to be located.
Further, temperature exchanges often occur along exterior facing walls, windows and doors, bringing interior temperatures closer to the temperatures outside of a building. These temperature exchanges or thermal energy losses increase the cost of operating HVAC systems in a building. As is known in the field of building construction, the use of insulating materials can decrease such temperature exchanges, but for existing structures, it may not be cost-effective to replace existing materials or add insulation within walls.
The thermal energy losses, both heat and cold, can be very substantial through windows in a building. The level of energy loss depends on several factors, including the quality of manufacture, materials used, and design. Windows can account for approximately 30% of the total thermal energy loss of a building. As the latest architectural practice calls for allocating at least 40% of exterior walls for windows, the potential for thermal energy loss can only increase.
The energy losses are inversely proportional to the thermal resistance R, meaning that the larger the value of R, the less energy will be lost.
The thermal energy losses for a particular material are directly proportional to the heat transfer coefficient K. For a single pane glass window K=0.96, but for double paned glass conventional windows K=0.27 for the windows, with the layer of air between the window panes having a K=0.024. It is evident from these values that adding an air blanket above the glass window will further reduce the energy losses by 0.27/0.024 or 11.25 times.
Conventional air curtains are commonly used in industrial applications where there is a need or desire to have open doors, while maintaining thermally distinct areas on each side of the door. An example of such use appears in at building entrances or cold storage rooms, where there is heavy truck or fork lift traffic in and out of the buildings or cold storage rooms.
Existing air curtains are high velocity blowers located in a large housing above the door producing substantial noise and requiring frequent cleaning and maintenance. Conventional air curtains are based on traditional electrically driven blowers located in the housing placed above the desired location. In addition to their bulk and being esthetically undesirable in the residential interior setting, these blowers are also noisy, require frequent cleaning and other routine maintenance as is usually required for high speed rotating machinery. Even a small amount of dirt on the surface of the high speed rotating rotor creates dynamic misbalance leading to high noise and eventual damage to or destruction of the unit. Existing air curtain systems are not feasible for use in residential or commercial office buildings. The proposed invention eliminates the problems of existing air curtain systems.
According to the present invention, the air circulated through the HVAC system is delivered into the interior of a building as an air curtain to prevent thermal energy exchanges between the interior and exterior of a building, and at the same time also uses the air curtain as a pollutant and insect barrier for open windows and/or doors.